Gambling games are unpredictable, sports betting types are more influenced by luck. We must admit that in the world of gambling, nothing is certain. Everything in the gambling world is very difficult to predict. Never expect too much because basically gambling is a way to get pleasure. We will not benefit because the main thing is to get pleasure and it is not an advantage in the form of money.
Yes, it is difficult to predict. However, for example in sports betting, there are statistics with players performance, history etc which can give you some indicators on what you will play. You describe gambling like it is something random, but it isn't. Playing with the odds is what makes gambling addictive and people stop being prudent and lose money.